1. Field of the Invention
The subject matter of the invention is an oil pump in a motor vehicle, having a housing, an electric motor arranged in the housing, and the electric motor drives a pump stage also arranged in the housing.
2. Description of the Prior Art
Such oil pumps are known and are thus prior art. The known oil pumps are positive-displacement pumps with correspondingly high power and volume flow rate. It is also known for oil pumps to be used in transmissions to drive oil circulation in the transmission. In the case of transmissions, it is known that the gear wheels dip into the oil sump, which leads to splashing losses during operation. To reduce the splashing losses, the oil level in the oil sump is lowered during operation by virtue of the oil pump extracting the oil and conveying it to a higher level in the transmission, wherein a volume flow must be managed with a relatively small pressure increase. It is a problem here that the known positive-displacement pumps are overdimensioned for this task, and thus ineffective, owing to their high power consumption. Furthermore, at low temperatures at which the viscosity of the oil greatly increases, the efficiency of a positive-displacement pump decreases further.